Unstable speeds from foreign locations with Cosmote LTE

[TuxPowered]

Hi,

Please forgive me if the topic is already discussed elsewhere, sadly I don't speak Greek and thus can't search the forum effectively.

At a rather remote location my Greek family has a holiday home and the only option for Internet connection is mobile broadband and the only available provider is Cosmote. They have the Gigamax Unlimited service (without 5G as it seems, tested with another 5G router). At the location I have installed Mikrotik LHG LTE 18. The *only* available BTS is 6km away but with direct visibility and the directional antenna of the Mikrotik router, it provides very good signal (RSRP -70 - -80dBm depending on primary EARFCN, SINR 20 - 25dB). Carrier Aggregation seems to work fine. The problem I'm facing is abysmal throughput, at least from foreign locations. Greek web seems to work fine, Youtube plays properly, Speedtest shows reasonable speeds (40-80Mb/s, limited by Wifi at the place), but foreign locations seem often very slow. And that's pretty bad, because I need non-Greek internet to work, when I'm at the location. To debug the issue I'm running my own Mikrotik bandwidth test server abroad over a symmetric gigabit connection (real datacenter colocation) and I'm testing download speed to the location in Greece. I ran the test with TCP over: public IPv4, public IPv6 and finally internal IPv4 tunneled over WireGuard (UDP over IPv4) and got very mixed results. When using a direct TCP connection it's either 100-200Mb/s (depending on which Carrier Aggregation is on) or below 10Mb/s. There's literally nothing in between. When the TCP stream is encapsulated in UDP I'm getting 100-200Mb/s *always*.

The issue does not seem related to time of day: by using different transport or protocol I can always get proper speeds.

Is this something known or expected at Cosmote? I've contacted their support (also for other issues) and never got any answer.

[K1m0n]

Is this something known or expected at Cosmote?

I have no issues accessing non-Greek internet with gigamax unlimited,
but my speeds are relatively limited (my only modem is an wAP AC lte6 which I use as travel router)
and its use is rather limited.
On some destinations tunneled trafic indeed seems to go faster,
so, I suppose the isp does do some sort of shaping.
What exactly isp does upstream no-one really knows.
I wouldn't expect stable bandwidth from lte, but 100/200->10 Mbps is indeed too excessive to be a reception issue.

That being said, in remote areas the usual problem is the limited capacity of the backbone
(but it doesn't look like so in your case).

So, idk.

Since its a mtik, I would try the latest ros + the latest modem firmware (<-note: different file/update vs ros).
Maybe lower lte mtu +clamp as a test too.

There is a thread ppl discussing about gigamax unlimited:
https://www.adslgr.com/forum/threads...extra-data-SIM

Ask there^, many have opted for lte/5G + an unlimited sim instead of xdsl,
and most have no issues.

- - - Updated - - -

updt:
now that I think it over, if /when you are measuring with a public ip (apn: vpn-internet),
that does come with a limiter @150/50 Mbps.
It doesn't explain your issue, but otherwise it's the highest you should expect.

[Kostinos]

First of all you must enable 5G through sending sms “5G” to 1333 with cosmote sim card
when you are on a foreign locations depend on so much things ex: trees wall of a house stone,Km of ant...
Outside of Greece for sure you need a VPN for faster response times...

[netblues]

First of all you must enable 5G through sending sms “5G” to 1333 with cosmote sim card
when you are on a foreign locations depend on so much things ex: trees wall of a house stone,Km of ant...
Outside of Greece for sure you need a VPN for faster response times...

WTF..
LHG LTE 18 is a 4g router, not 5g
So trees and stones make international Internet slow, but not regional., right?
And no, we do not live in China and nobody needs a vpn for faster response times.
As for public internet apn this would have to be enabled by special request, and is also irrelevant to the speed issues reported.


It seems the op does have some issues which are specific to his location. Interference? Strange CA settings, can't tell
There is definitely no carrier side reason for all this.

Perhaps you could try tethering with a phone and see if you get more stable behaviour, (albeit slow)

[Kostinos]

WTF..
LHG LTE 18 is a 4g router, not 5g
So trees and stones make international Internet slow, but not regional., right?
And no, we do not live in China and nobody needs a vpn for faster response times.
As for public internet apn this would have to be enabled by special request, and is also irrelevant to the speed issues reported.


It seems the op does have some issues which are specific to his location. Interference? Strange CA settings, can't tell
There is definitely no carrier side reason for all this.

Perhaps you could try tethering with a phone and see if you get more stable behaviour, (albeit slow)

He said that it test it with 5G router,but never said if send the sms to 1333...
I know mikrotik LHG is 4G router...
He said that it have issues outside of Greece Cosmote need a lot of work with exchange points right now sending traffic to Germany even if he can send it to Bulgaria... the only way to solve that, is using a VPN...

[fadasma]

Since you have faster connection over WireGuard, then why don’t you stay that way and use the MikroTik as your exit node to route all traffic through?

[TuxPowered]

> He said that it test it with 5G router,but never said if send the sms to 1333...

Yes, I had with me a 5G router Zyxel NR7101 and this Mikrotik LGH LTE 18. Sadly I had no idea about the 1333 SMS and my Greek family did not know either. However I did test it with my non-Greek SIM card in roaming and the results were not very good. The place is quite far away from the BTS, I assume that LTE with good signal works better than a single 20MHz-wide 5G channel with weak signal. Mikrotik with LTE provided better bandwidths. Until it didn't. But this happens only occasionally, so I have not noticed immediately.

I've opened a support case with Mikrotik and also from my own observations I thought the issue is with CA not enabling. But now I'm not convinced anymore, as I have configured the LTE modem to only use band 1 where is only a single channel, so CA is not possible. The results are the same. UDP streams work fine, albeit slower than with aggregation, TCP streams occasionally drop to single Mb/s.

> when you are measuring with a public ip (apn: vpn-internet)

That is the next thing I want to try. Is this available to everybody with the Gigamax contract or do I need to send some SMS again? Cosmote is definitely performing some magic for TCP connections. Traceroute over tcp is definitively fake with just 4 hops. Real traceroute over ICMP to the same host is 17 hops.

[9:39:34] # sudo mtr -wrc10 --tcp -P 80 heise.de
Start: 2023-11-26T09:39:41+0200
HOST: MB-20001482         Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 192.168.93.1         0.0%    10    3.0   2.9   2.3   3.5   0.4
  2.|-- ???                 100.0    10    0.0   0.0   0.0   0.0   0.0
  3.|-- 10.24.6.241          0.0%    10   30.2  28.4  16.9  52.1  11.1
  4.|-- redirector.heise.de  0.0%    10   25.2  24.9  16.1  41.3   7.5

- - - Updated - - -

> Since you have faster connection over WireGuard, then why don’t you stay that way and use the MikroTik as your exit node to route all traffic through?

That would work for me when I'm working remotely from the location, but not for my Greek family. Suddenly getting German ads on Youtube, having 120ms latency on video calls back to Greece. Not the best Internet experience

[ariadgr]

> when you are measuring with a public ip (apn: vpn-internet)

That is the next thing I want to try. Is this available to everybody with the Gigamax contract or do I need to send some SMS again?

The owner of the contract needs to call customer services (13888 free from OTE landline, or with a one-off charge from Cosmote mobile, or +306971013888) and ask for vpn-internet to be enabled for this line.
If asked for details, say you have cameras you need direct remote access to.

[xristostsilis]

is there any possibillity that your antenna hops over to other cell tower randomly and comes back to the main one? Can you try band or even cell lock to be sure. Yes also call 13888 and ask for enabling the APN: VPN to have a public ip and see if that helps

[TuxPowered]

> is there any possibillity that your antenna hops over to other cell tower randomly and comes back to the main one

The place is in a valley with only this tower visible. The LTE router has a directional antenna pointing directly at that tower. There are only 2 Cell IDs from that tower which the router switches between, one facing us directly with -70dBm signal with up to ~200Mb/s download, the other one facing slightly off (according to cellmapper.net), providing only -90dBm with up to ~100Mb/s download. I have Grafana graphs for this and over the last month I've seen the router connecting *once* for one hour to a 3rd Cell ID, which is from the same tower too. Apart from that it stays very stable, using just 2 Cell IDs, often for hours long on each one.

> Yes also call 13888 and ask for enabling the APN: VPN to have a public ip and see if that helps

That is my last resort, also maybe this way I could get Cosmote's attention. Tickets opened via the web form remain unanswered. Unfortunately the contract is not in my name and I don't expect the family there to be able to explain what's going on.

[TuxPowered]

The mystery is solved. Disabling "COSMOTE Mobile Security" package resulted in TCP connections working perfectly fine. Caveat: it had to be disabled from https://my.cosmote.gr/selfcare (which I could do only once I finally came to Greece, a few months after opening this topic). It should be possible to do it by sending SECOFF to 1256 (which I've tried multiple times while managing the network remotely), but even thought I got back an SMS stating that it's already turned off, there was no change in behaviour. Even worse, I learned about this security package and found out that disabling it via SMS didn't work because it occasionally redirects valid requests to Cosmote's (well, technically Ookla's) speedtest servers (which serve random data pretending to be a JPG) to some captive portal warning me about insecure content.

[K1m0n]

Disabling "COSMOTE Mobile Security" package resulted in TCP connections working perfectly fine.

Well.. thats a new one, well done anyway.